This invention relates generally to radio paging systems and more particularly to a two-way radio personal data message system in which a miniature transceiver is carried by an individual for presentation of messages to that individual and for transmission of messages to a central site for relay to another individual or to a data base. Several central sites may coordinate their operation such that messages may be relayed between sites and follow a particular pager from one central site to another. Interconnection between the central sites and data communications networks enable the exchange of messages between the remote pager units and external data message generators and data bases.
In a desire to satisfy the need of individuals who must be away from their base of operations to communicate with their base, several types of radio communications systems have been developed. A traditional form of radio communication utilizes a base station transceiver located at a site of favorable radio propagation and a number of transceivers mounted in vehicles for communications in a manner such as the familiar two-way radio police communications. Another form of radio communications is a mobile telephone service, which allows interconnection with the extensive public switched telephone network (PSTN) and affords the availability of the mobile telephone user to everyone who has a telephone. Mobile telephone and two-way radio equipment, however, is generally large, heavy, and unlikely to be carried with the user at all times. Because of this, the advantages of mobile telephone and two-way radio are diminished.
Portable cellular radiotelephones offer excellent two-way communications services which exceed the needs of pager users at a higher cost commensurate with the services. Real time voice (or data) is not always desirable to an individual who wishes only to have a message taken without having a current activity disturbed.
Pagers have been and continue to be, in their simplest form, miniature receivers which are well known by the general public and those skilled in the art. These devices are generally tuned to a particular radio frequency which is shared with many other pager users and which is typically modulated with tones or data bits. A particular sequence of tones or data bits is used as an address or identification for one particular pager or a group of pagers of the many monitoring the radio frequency. Reception of the particular sequence activates an acoustic, visible, or tactile alert thereby indicating a call has been made to that pager (generally from a telephone connected to the PSTN). Depending upon the equipment and system complexity, the pager may receive a voice or data message following the alert or the alert alone may simply indicate to the user that a call was made and a prearranged action, such as to telephone a specific telephone number, should be taken. More recent developments have allowed data messages to be stored in a memory within the pager and recalled at the user's convenience.
Pagers have also evolved into devices which can transmit in addition to receiving. Complex telephone answering devices have demonstrated the ability to answer a telephone call, alert a user via a pager, collect a message from the telephone caller, and relay it to the pager. Advanced forms of telephone-answering device pagers offer the user the ability to transmit an acknowledge from the pager to the answering device thereby causing the device to take a particular action such as to return a tone to the telephone caller indicating reception of the call. This predetermined response, however, offers a limited repertoire of responses over a limited geographic distance.
Most pager users, however, wish to move about freely and have their pager respond to messages and generate messages without regard for radio coverage areas or distance from the base station. Telephone answering devices provide coverage ranging to a hundred meters or so while a commercial shared paging service with an optimum transmitting site may provide coverage as much as 100 kilometers from the site. More extensive networks of simulcast transmission provide shared service users an even greater area of coverage than a single transmission site can provide. The advent of satellite communications makes possible a nationwide linking of shared service systems into a national paging network. It has also been proposed to angle modulate high power AM broadcast stations with paging information and conceivably signal pagers 1000 kilometers from the station.
Data communication systems, networked with each other and covering large areas and many terminals, are well known and extensively described in the literature. One highly prevalent system couples messages generated at one terminal through a local mode, or local data controller for a number of terminals, which routes the message to another local mode for distribution to a second terminal using an address embedded in the message for routing instructions. A more sophisticated system utilizes one or more central message processors to control the routing of the message and may be reprogrammed to allow the terminals to be moved about the system. The problems faced when the terminals are highly mobile and connect to the local mode or central site via a radio channel compound the complexity of the location algorithm and require data transmission techniques different than those used in traditional data networks.
Electronic mail services provide message services for terminal users who may log on to a timesharing system and request messages which have been stored at the timesharing computer site from any place which has a telephone or other means of connecting to the timesharing system. The disadvantage of this technique is that there is no indication to the user that a message is being held. The delivery of the message must wait until the user logs on at some location and receives a message-held indication from some central site.
A dynamic communications system roaming user location technique has been described for mobile telephone systems and in particular for cellular radiotelephone systems which may provide country-wide radiotelephone service. In these systems, the radiotelephone user may preregister in a radiotelephone area other than the "home" area (normal service and billing area) for service to be provided in the other or "roam" area. When the user arrives in the roam area, the radiotelephone is qualified to make radiotelephone calls and has calls which are received in his home area forwarded to the roam area for transmission to the user. If sufficient data links are available, the roaming qualification may be automatically performed when the roaming radiotelephone appears in the roaming area and the user initiates a first telephone call. The roaming radiotelephone identification is entered into a list of roamers in the home area so that incoming calls to the radiotelephone are forwarded to the roaming area. If, however, the roaming radiotelephone is out of range or turned off or if the user is not close to the radiotelephone, the user cannot receive a call and generally has no notion that a call was attempted.
Thus it has been shown that it is possible to create a nationwide service for sending messages to individuals. Ideally such a service should make every effort to convey the message to the user and provide the user every possibility of generating and transmitting a message. Pagers, because of their physical dimensions, tend to remain with their users more often than other communications devices and can be used for generating and transmitting messages in the more advanced devices. It has not been feasible, until the present invention, to coordinate the radio pager and the supporting system into a nationwide network which can ensure a conveyance of a message to the radio pager and accept messages and acknowledgements from a radio pager wherever in the system the pager might be located.